New York State Museum Bulletin (Volume 184-187)

Book may have numerous typos, missing text, images, or index. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1916. Excerpt: ... "secondary jaws" and " suboral epineurals." On the supposition, however, that P. narrawayi presented an apical aspect, these plates presented much difficulty, for, so far as known, this type specimen is the only fossil sea star showing two pairs of floor plates one over another and with their common faces meeting in the same interradial vertical plane as those of the first pair of cover plates or between what is commonly called the "adambulacral jaw" and the apical skeleton. The apparent direction of their movements would seem to aid in thrusting food out of the oral cavity, not into it. They may have become double chains of ossicles connecting the apical surface of the axillary interradial with the first cover plates and, by means of muscular attachments, serving to draw the latter apically, but whatever function we assign them (and their form hardly allows us to regard them as vestigial and functionless) we must admit that they no longer represent a primitive' condition. Although Schuchert (1915, page 34, figure 1) gives a ventral view of a "Theoretic Phylembryo of Stelleroidea. . . . Based on Hudsonaster," he pays no attention to the peculiar features noted above but draws his first floor plates as he finds them in U raster e 11 a girvanensis. If Hudsonaster is at all like'Protopalaeaster, only four floor plates could be seen beside the first si* cover pieces drawn. The latter also iri both Hudsonaster' and Urasterella are never set exactly opposite the floor plates but slightly nearer the oral aperture. References . Bather, F. A. 1900 The Crinoidea in Lancaster's, "A Treatise on Zoology" Adam and Charles Black. London. -- 1915"' Studies in Edrioasteroldea I-IX. The '" author. "Fabo,"" Marryat Road, Wimble ' ... j?ng F...